Several existing devices, such as a fluorescent light tube, emit considerable quantities of noise in the millimeter frequency bands. This knowledge is used in creating noise sources for evaluating the operation of receiving devices that are designed to operate against targets which can be detected upon the basis of a noise differential between a target noise energy level and the energy emitted by surrounding background. Typically, a target may be a vehicle such as a tank or aircraft and background may be woodland, desert, buildings, and sky.
A conventional energy source using a fluorescent light tube has been used as a simulation device to test passive receivers. When the passive receiver is located in a missile frame that is intended to home on a target based upon emitted energy differences between the target and its immediate environmental background, it is necessary to control the intensity of background radiation and the position or relative location of the source of this radiation when simulating environmental background. In this conventional noise source, the emitting element is an individual flourescent light tube that is mounted along an axis that lies between the focus of a parabolic reflector and the center of the parabola. Thus a distributed line source is created in front of a parabolic reflector. However, a distributed line source provides a variety of energy paths due to its defocused nature. Additionally, when placing more noise radiating elements on a simulator board, the parabolic reflector is modified to the point where, when viewing the reflector from the front, it appears to be substantially square. This design expediency causes a wavefront configuration that is almost impossible to accurately define at any given point. Energy emitted from each elemental unit (fluorescent tube-parabola combination) is controlled by varying the current through the particular fluorescent tube. At low electric current levels, required to simulate correspondingly low levels of radiation, the emitted energy of a fluorescent tube becomes erratic. This does not provide an adequate range of energy change to reasonably simulate the range change or background radiation experienced by a missile during a terminal mode of flight. Movement of an emitting source is simulated by reducing or eliminating the electrical power provided to the fluorescent lights, which in turn reduces or eliminates the noise energy transmitted in millimeter bands to establish a simulated target background energy difference pattern.